Copper-Nickel alloys: properties, GOST. Production of copper-Nickel alloys. Cleaning of coins from a copper-Nickel alloy

Copper belongs to the group of non-ferrous metals. In its pure form it has high thermal and electrical conductivity, it is therefore used mainly in electrotechnical production. Copper – very plastic material, which responds well to pressure treatment in cold and hot conditions.

To enhance the mechanical, engineering and operational properties of copper uses of its compounds with other metals. As a result of the fusion process changes the structure of crystal lattices, there are additional relationships between ions and atoms. It increases the strength of alloy compared to pure metal.

What is copper alloy with Nickel

With fusion Nickel is the main alloying element. It has corrosion resistance, so are mainly used for hardening. When alloying it with copper are formed of continuous solid solutions. Copper-Nickel alloy acquires a number of new features:

• Increases the resistance of the material;
• Significantly reduced temperature coefficient of electrical resistance;
• There is a high resistance to corrosion, especially in seawater.

Classification

Properties of copper-Nickel alloy depend on the percentage of its Nickel and other substances. Currently created a lot of new special materials with unique characteristics.Depending on the area of application they are divided into structural and electrical.

• Structural - have high corrosion and strength characteristics. Their products are resistant to aggressive environments. This cupronickel, Nickel silver and cunial. A separate place in this list is Monel, which is proportional to the ratio of the elements are somewhat different.
• Electrical - have an increased electrical resistance and thermoelectric properties, using them in power engineering and electrical engineering. This is Constantan, manganin and Copel.

Knowledge of the chemical composition and physical characteristics allows to determine the copper-Nickel alloy to one of the groups.

Melchior

Contains about 80% copper, 20% Nickel, and some manganese and iron. A similar alloy was known to people even in the third century BC under the name of “white copper” thanks to a light silver colour, resembling silver. It has high anticorrosive properties, as well as a large reserve of strength and wear-resistance copper-Nickel alloy. melting point - approximately 1170 °C. Good ductility allows products of pressure. Used in the manufacture of capacitors, it is made from medical instruments, inexpensive jewelry, silverware, coins.

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German silver

This copper-Nickel alloy with additions of zinc, which is silvery with a greenish hue. Depending on the brand can contain up to 35 % Nickel and 45 % zinc, the rest – copper. Such a solid content of zinc significantly reduces the cost of its production. Nickel silver has approximately the same mechanical properties as the Nickel silver. It is corrosion resistant, durable, ductile enough to handle in hot and cold state by pressure.

Sometimes additional legarrette lead for better machining. Mainly from it produce the details of the devices, watches, medical instruments. Interestingly, due to the low cost now because of it, more often than of Nickel silver to produce jewelry, medals and orders. Nickel silver is also used in the manufacture of enamel.

Kunal

Consists of a copper base, Nickel - up to 20 %, small additions of aluminum. Is fused at a temperature of 1183°C followed by quenching and aging, resulting in very high strength and resistance to low temperatures. Divided into grades A (MNA13-3) and B(MNA 6-1,5).
Mark And has two important characteristics-high toughness and unique resistance to corrosion in aggressive environments. For example, in sea water it can be operated for decades. Therefore, the alloy is used for the manufacture of parts (propellers).

Grade B has springing properties, so is widely used for the manufacture of elastic elements for critical applications. It is also highly resistant to breaks in the cold. It produces structural parts, operating in conditions of low temperatures.

Monel

It contains about two-thirds Nickel and one third copper. The melting temperature is 1350 °C. the Main property of this copper-Nickel alloy-corrosion resistance. It has high performance mechanical properties-strength and plastic deformation. Monel brand Nmims contains about 28% copper, 3% iron, about 3% magnesium, a small amount of cobalt and Nickel.

Same features of Monel-400. It is a trademark of the Special Metals Corporation and was patented in 1906. So other manufacturers can't use this name. So there is another alloy – Nicorros. However, these materials are identical in all chemical and technical characteristics.Since the alloy contains more than halfNickel in percentage terms, its cost is quite high. However, there is a production technology of copper-Nickel alloy using raw materials from natural sulfide ores containing both elements, without prior separation into individual components. This can significantly reduce the cost of the final product.

Monel is used for the production of products ekspluatiruemykh in aggressive environments, conditions of high mechanical loads. The shipbuilding, chemical and petroleum industry, manufacture of medical instruments, critical parts of machinery and apparatus.

Constantan

Is white with a characteristic yellowish swallowed. The set includes: copper -59 %; Nickel – 39-41 %; manganese-1-2 %. The melting temperature 1260 °C. This copper-Nickel alloy got its name due to the primary property – of thermal stability. He has a very good performance of electrical resistance at a low value of temperature coefficient of expansion. Alloy is for the production of wire for thermocouples in the production of measuring instruments, and also electric heating elements operating at temperatures up to 400-500 degrees.

The Wire made of Constantan, is subjected to special heat treatment in which the metal surface forms a thin oxide film. Due to this, the product does not require additional paint or protective coating. Constantan is very plastic. This property allows it to be used when welding copper-Nickel alloys.

The Disadvantage of Constantan is its rather high EMF is about 43 mV. This eliminates the use of wire and tape of him in high-precision measuring instruments.

Manganin

It Contains about 5% Nickel, 12% manganese, and the basis of copper. The melting temperature is 960 °C. it is Interesting that the manganin was invented by the American Edward Weston in about 1888, based on they invented the Constantan as a special material for the windings of electrical appliances. He really has high electrical resistivity and extremely small EMF in a pair of copper (less than 1 mV), which distinguishes it from Constantan.

In order to reduce the temperature coefficient of resistance, manganoui wire is annealed at temperatures of about 600 degrees in a vacuum and then slowly cooled. This technology allows to increase the temperature at which a material maintains its electrical properties up to 200°C. the Already wound coil wire is repeatedly heated further to 150 °C. this achieves the effect of artificial aging, after which changes in the crystalline structure of the metal is minimized.

The Main scope of manganin as a material with a stable performance of the electrical resistance - production of a variety of high precision instruments for the measurement of electric current (amperage, voltage, power).

Copel

Another special alloy. Contains copper, 43% Nickel, some iron and manganese. Melting point 1290 °C. Due to optimum ratio consistently low resistivity and high TEDS paired with a variety of metal alloy used for the manufacture of wire for thermocouples and electrodes. Indicator TEDS material increases the operating temperature:

• At 100 degrees Celsius - to 6.95 In;
• 600 - up to 49V.

Coppel very heat resistant - without violating the basic properties withstands heat up to 600 degrees and is resistant to corrosion.
Beads used in the thermocouple sensors of devices for contactless temperature measurement. They use thermocouples with maximum TEDS – with chromium, copper or iron, These elements are positive electrodes, and Kopel –is negative. Thermocouple Copel-chromel is mainly used in pyrometry for continuous temperature control in the range from 200 to 600 degrees in industrial and laboratory installations.

Smelting Process

In the production of copper-Nickel alloys stick to a relatively similar technologies. Cupronickel, Nickel silver, cunial, Constantan, manganin first smelted in induction furnaces under a layer of burnt charcoal. Adding to the mixture of waste allowed up to 80%.

The Process begins with the smelting of copper and Nickel. As they melt are added the waste is in large pieces then smaller ones. Last loaded zinc. After the final melting of the charge produces the deoxidation with manganese and silicon (Nickel-silver) or silicon and manganese (Constantan and Nickel silver). After that, the surface of the melt clean up slag and add more charcoal. Heat the molten mass to a temperature of about 1300 °C, with addition of manganese chloride for refining.

Slightly different technology of preparation of kunala, as they contain aluminum. Before the introduction of aluminium in the melt must be added to 0.1% manganese for deoxidation. And after the dissolution of the aluminium melt surface sprinkled with flux. If this is not done, formed films, from which the melt becomes unfit to fill.

Chemical, physical and structural properties determine the destination area of the various copper-Nickel alloys. GOST 492–73, GOST5063–73, GOST 5187–70, GOST 5220–78, GOST 17217–79, GOST 10155-75 are the major standards in their production.

Coinage

Around the end of the nineteenth century generally began to mint coins of copper-Nickel alloy. Its Composition is strongly varied at the different mints. But mostly he kept to 30% of Nickel, a minor admixture of iron and copper as the basis. As the metal for the usual coins should be primarily ductile, malleable, durable, and inexpensive, practical way was constituted coin alloy. Subsequently, the particular popularity for the manufacture of the coins used by Melchior.

Modern Russian coins are made of various alloys. In particular, completely made of Nickel silver consists of coins that were released before 2009. Steel coins of one and five cents and five-ruble copper covered with a thin layer of Nickel silver. This material is called “the bi”. So more decreases the cost of manufacturing of metallic money.

The Alloys of copper with Nickel, is not subjected to air oxidation. Therefore, its characteristics can be found only on old coins, or those that had long been in a hostile environment. Some expert treasure hunters and coin collectors are used to clean valuable specimens of coins of various tools – from traditional recipes to cutting edge technologies.
Clean up with soap and water removes well only greenish copper oxides. Also used olive oil, acetic acid, paste "Goya". You need to keep in mind that these funds can not only remove plaque but also to react with the alloy itself, causing harm to the coin. The most effective, economical and rapid is the cleaning of coins from a copper-Nickel alloy by electrolysis.